This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The transcription factor TFIID, composed of the TATA box binding protein (TBP) and 14 TBP associated factors (TAFs), plays a key role in regulation of gene expression by RNA Polymerase II. TFIID plays a critical role as a core promoter recognition factor that begins the process of assembling the transcriptional apparatus at the start site of protein coding genes in eukaryotes. A variety of biochemical studies of TFIID complexes have suggested that the largest subunit of the complex, TAF1, possesses histone acetyl-transferase and kinase activities that may play critical roles in the regulation of gene expression from TFIID dependent promoters. While these activities have been postulated, TAF1 domains possess no sequence homology with any known kinase or acetyl-transferase family members. Although some TAF1 domains and functions have been characterized, the largest C-terminal region of the TAF1 molecule identified as the likely enzymatic domain remains structurally unknown. Consequently we are interested in obtaining structural information for the TAF1 subunit of TFIID. We have previously identified a stable subcomplex of TFIID that consists of the putative catalytic region of the TAF1 subunit and the regulatory region of TAF7 and have determined conditions for the expression and purification of this complex from E. coli. We hope to determine the structure of the TAF1-TAF7 subcomplex of TFIID crystallographically and believe this will provide the first structural glimpse into the organization and assembly of the preinitiation complex.